But Anthropic isn't paying for the electricity and cooling. They don't run their own data centers, they rent compute from providers who cover those costs.

That's entirely why they can blow compute on the fun projects like this. If they had to pay extra for the electricity, they wouldn't do it.

Most of the GPU cost is in the GPUs themselves (and in the space and maintenance costs of the building). Electricity is a small fraction, and it's not like datacenters are just going to shut down their servers when they're not in use.

There is cost, but the cost is mostly the opportunity cost of not being able to do something else.